The present invention relates to a medical instrument for dissecting tissue in the human or animal body.
An instrument for dissecting tissue is one used for cutting and for grasping tissue, for example a punch, a pair of scissors or a forceps.
Instruments of this kind are used in the context of minimally invasive surgery for dissecting tissue in the human or animal body, usually under endoscopic monitoring. To this end, instruments of that kind comprise an elongated shaft which has at least one movable tool arranged at its distal end, which usually coacts with another movable or immovable tool, arranged at the distal end of the shaft, for dissecting the tissue. For operating the at least one movable tool, such instruments are further provided, on the proximal end of the shaft, with at least one movable grip element through which the axially movable force transmission element, transmitting thrust and/or pull forces, is non-positively connected with the at least one movable tool so that any movement of the movable grip element is translated by the force transmission element into a movement of the movable tool.
Especially for operations in the region of the ear, nose and throat one normally uses instruments with a shaft having at least one bend in order to permit the tool or tools arranged on the distal end to be advanced to positions that are accessible only with difficulty, for example into niches in the frontal or the maxillary sinus.
An instrument with a bent shaft, especially if the bending radius is small, presents the problem that the force must be transmitted by the force transmission element from the movable grip element through the bend to the movable tool. This is rendered difficult especially in view of the aim to have a slim instrument, i.e. one with a thin shaft.
In order to be able to adapt itself to the bend, the force transmission element must, therefore, be flexible in the region of the bend of the shaft.
DE 44 44 025 A1 discloses, for example, a force transmission element for a medical instrument in the form of a flexible wire element, which is capable of adapting itself to such a bend. However, a flexible wire can transmit only tensile or pull forces, but is not suited for transmitting thrust, or even high thrust. For, if the force transmission element is subjected to thrust, the wire will buckle so that only small, or no thrust can be transmitted to the at least one movable tool for actuating the latter for the purpose of dissecting tissue.
Considering, however, that such instruments are also used for cutting hard tissue, for example cartilage or bone tissue, the nature of the force transmission element must be such to permit even very high forces, especially high thrust forces, to be transmitted to the movable tool without any buckling of the force transmission element, and this, of course, although the transfer of forces must be effected through the bend of the shaft, which means that the force transmission element must be capable of adapting itself to the bending radius during its axial movement.
DE 195 20 717 C2 proposes to solve this problem with the aid of a tubular-shaft instrument with a tubular shaft provided with a bend, where the force transmission element is arranged inside the tubular shaft. In the bent portion of the tubular shaft, the force transmission element is configured as a bar made from a flexible material, which is in contact with the inner wall of a surrounding rigid sleeve, extending concentrically to the shaft, and whose cross-section is reduced, in the region of the bend, by a number of circumferential grooves arranged one beside the other in axial direction. The before-mentioned sleeve may be constituted also by the tubular shaft as such. The circumferential grooves are formed to extend over the full circumference of the bar. Thus, the bar is locally reduced in thickness to sort of a wire with circular cross-section in the region of the circumferential grooves. In the intermediate sections between the grooves, the diameter of the bar is not reduced so that the outer surfaces of the intermediate sections serve as guide surfaces to guide the force transmission element in the region of the bend in contact with the inner wall of the sleeve and/or the tubular shaft.
Although such a force transmission element permits high thrust forces to be transferred through the bend to the movable tool, this known instrument nevertheless must be regarded as disadvantageous with that configuration of the force transmission element.
Considering that such instruments are used in minimally invasive surgery, it is another demand that must be placed on such instruments that their diameter in the region of the shaft be as small as possible to permit the instrument, together with the shaft, to be introduced into an incision or natural opening in the body which should be as small as possible. In the case of such miniaturized instruments with a shaft diameter of a few millimeters only, this means for the known instrument that the force transmission element has an extremely small diameter in the reduced regions of the circumferential grooves, whereby the stability of the force transmission element is reduced because the material thickness of the force transmission element is reduced to very small wire cross-sections in the region of the circumferential grooves. Therefore, the force transmission element may buckle or break in the region of the circumferential grooves extending over the full circumference when high thrust or sudden thrust is transferred, or may fracture when high pull forces are transferred, whereby the operating safety of the known instrument is reduced.
DE 43 00 064 A1 discloses a punch for dissecting tissue having an outer shaft and an inner shaft, at a distal end of which an opening having a blade is provided, which coacts with a counter blade at the distal end of the outer shaft in such a way that, upon actuation of the punch, tissue which protrudes through said opening in the inner shaft, is cut off by the blades moved against each other. The inner shaft is formed rigid, is straight in the proximal region and merges distally into a curved course, and the outer shaft, which forms the force transmission element of this instrument, is at least in the region of this curvature deformable. The deformability of the outer shaft is made possible by that the outer shaft is provided with recesses which face each other on the radius of the curvature of the inner shaft. The recesses in form of radial incisions or notches only leave a narrow bridge of material between themselves.
U.S. Pat. No. 5,507,772 also discloses a medical instrument, the shaft of which comprises a bend. The force transmission element comprises a plurality of notched or recessed sections in the region of the bend of the shaft. Between the recessed sections of the force transmission element a plurality of ribs are formed, the thickness of which substantially conforms to the thickness of the remaining body of the force transmission element. The ribs are formed in direction of one side of the force transmission element only, whereas the force transmission element is configured continuously flat in the region of the bend on the opposite side of the ribs. The force transmission element and the ribs thereof are guided in an elongated slot inside the shaft, which slot is provided in the concave inner side of the bend of the shaft. In another embodiment, the ribs are omitted so that, in this case, the force transmission element is configured in the region of the bend as a flat band, which, however, is not guided in this case.
U.S. Pat. No. 4,646,745 further discloses a medical stapler, which comprises a force transmission element disposed within said shaft, wherein the force transmission element is configured in form of a flat band, so that the force transmission element is flexible. The flat band itself consists of three sheets of thin bands. In the region of a bend of the shaft, the flat band is guided along a spacer element, in order to achieve that the flat band maintains its central position in the shaft in the region of the bend, if the flat band is under tension, i.e. in order to prevent the flat band from becoming straight in the region of the bend of the shaft. The spacer element is provided with ball bearings for reducing the friction between the force transmission element and the space element.
Now, it is the object of the present invention to improve a medical instrument of the before-mentioned kind in such a way that high pull and/or thrust forces can be transferred to the at least one movable tool by means of the force transmission element, through the bend of the shaft, without any buckling of the force transmission element and without any reduction in stability of the force transmission element being encountered in the region of the bend.
In a first aspect of the invention, this object is achieved according to the invention by a medical instrument for dissecting tissue in the human or animal body, comprising:
a shaft having a distal end and a proximal end, said shaft having at least one bend between said distal and said proximal end;
at least one movable tool disposed at said distal end of said shaft;
at least one movable grip element disposed at said proximal end of said shaft;
a force transmission element having a distal end a proximal end and extending along said shaft and, further, being movable relative to said shaft, said proximal end of said force transmission element being operatively interconnected to said at least one movable grip element and said distal end of said force transmission element being operatively interconnected to said at least one movable tool for transmitting a force from said at least one movable grip to said at least one movable tool,
wherein said force transmission element is configured, at least in the region of said bend, as a flexible tubular element conforming to the bend, which is guided in contact with said shaft, and wherein said tubular element is configured as a helical spring with closely wound windings.
Consequently, it is provided according to the first aspect of the instrument according to the invention that the force transmission element is configured, at least in the region of the bend, as a flexible tubular element in form of a helical spring, which is guided in contact with the shaft. It is an advantage of such a flexible tubular element that it can be made from material of substantially the same thickness throughout. By having the flexible tubular element guided in contact with the shaft, in the region of the bend, the tubular element is prevented from buckling because any lateral deflection of the tubular element during transfer of thrust forces is rendered impossible by the guiding relationship between the element and the shaft. The configuration of the force transmission element of the instrument according to the invention is suited both for cases where the force transmission element is arranged inside a shaft configured as a tubular shaft, and for cases where the force transmission element as such is configured as tubular shaft and guided on the outside of the shaft. Due to the fact that the tubular element can be given the same material thickness over its full axial length, thinner regions as encountered in the known instrument, where the force transmission element is reduced to the shape of a wire in the regions of the circumferential grooves, are avoided whereby higher overall stability and, thus, improved operating safety of the force transmission element and, thus, of the whole instrument is achieved.
The configuration of the flexible tubular element as a helical spring is of particular advantage because a helical spring, consisting of steel, for example, is rigid in radial direction but presents high elasticity along its longitudinal axis because the windings of the helical spring a capable of moving one relative to the other when the helical spring is bent. By giving the helical spring closely wound windings, high thrust forces can be transferred by the helical spring to the movable tool, without any loss of force and without delay, because the helical spring cannot be compressed in axial direction.
According to a further preferred embodiment, the force transmission element is configured as a tube comprising the tubular element in the region of the bend, the tube being arranged around the shaft.
This feature, namely the external arrangement of the force transmission element relative to the shaft, provides the particular advantage, especially in the case of miniaturized instruments with small shaft diameter, that the shaft as such can be given a relatively narrow overall shape, whereas a larger diameter is available for the force transmission element. It is thereby possible to provide an especially strong force transmission element, suitable for transferring high thrust and pull forces, even with instruments of particularly narrow overall shape.
According to a further improved embodiment, the shaft comprises a solid bar made from solid material.
It is an advantage of this feature that due to the configuration of the shaft as a solid bar a particularly strong instrument body is obtained that gives the instrument particularly high stability against bending stresses exerted on the shaft.
It is further preferred if the tubular element is connected with the remaining tube by a substance bond.
This feature is of advantage in terms of easy manufacturability of the force transmission element since the tubular element, especially if in the form of a helical spring, and the remaining tube of the force transmission element can be manufactured by separate processes and can be connected thereafter by soldering, welding or bonding. Another advantage of that feature lies in the fact that the helical spring and the remaining tube constitute a single component, which facilitates the assembly and disassembly procedures of an instrument that can be taken apart to its shaft and force transmission element.
According to a further preferred embodiment, the tubular element is directly connected with the movable tool.
It is an advantage in this connection that in cases where the bend is arranged close to the distal end of the shaft an instrument can be realized that has a short axial length on the distal side of the bend.
According to a further preferred embodiment, the movable tool is connected with the remaining tube in non-positive fashion, by means of a flexible pull element parallel to the tubular element.
It is an advantage in this connection that even high tensile or pull forces can be transferred over the bend, the tensile forces being then absorbed by the flexible pull element, whereby it is additionally avoided that the tubular element, if in the form of a helical spring, will expand axially under tensile stress exerted on the force transmission element, so that it is always guaranteed, also when tension is transferred, that the movable tool is properly entrained. The pull element may in this case take the form of a band, a wire or a strand made from metal, carbon fiber or Kevlar.
It is further preferred in this connection if the shaft comprises a groove, in the region of the bend, in which the pull element is guided between the tubular element and the shaft.
This arrangement provides the advantage that the pull element, too, is guided and retained with little play over the bend, between the helical spring and the shaft, during axial movements of the force transmission element.
According to a further preferred embodiment, the pull element is directly connected with the at least one movable tool.
This feature advantageously guarantees that the at least one movable tool is moved any time a tensile force is exerted upon the flexible pull element.
According to a further preferred embodiment of the instrument according to the invention, the shaft and the force transmission element are detachable from each other.
It is an advantage of this arrangement that contaminants that may collect in the region of the tubular element and also in the remaining region of the shaft, between the force transmission element and the shaft, can be removed easily and safely whereby the cleaning properties of the instrument according to the invention are improved.
In a second aspect of the invention the object underlying the invention is achieved by a medical instrument for dissecting tissue in the human or animal body, comprising:
a shaft having a distal end and a proximal end, said shaft having at least one bend between said distal and said proximal end;
at least one movable tool disposed at said distal end of said shaft;
at least one movable grip element disposed at said proximal end of said shaft;
a force transmission element having a distal end and a proximal end and extending along said shaft and, further, being movable relative to said shaft, said proximal end of said force transmission element being operatively interconnected to said at least one movable grip element and said distal end of said force transmission element being operatively interconnected to said at least one movable tool for transmitting a force from said at least one movable grip to said at least one movable tool;
said force transmission element being configured, at least in the region of said bend and at least sectionally transversely to a plane of curvature of said bend, flattened and flexible, and said force transmission element extending in the region of said bend in the direction transversely to said plane of curvature of said bend continuously in axial direction at least over an inner diameter of said shaft, and said force transmission element comprising a plurality of axially spaced flattened sections,
wherein said force transmission element is in contact by its circumference with said shaft in intermediate sections between said flattened sections, and wherein said intermediate sections extend to both a concave and a convex inner side of said bend of said shaft.
With an instrument comprising a shaft in the form of a tubular shaft and a force transmission element arranged inside the tubular shaft, it is provided to give the force transmission element a locally flattened flexible configuration in axial direction, at least in the region of the bend. Flattened means in this connection that in the flattened region the force transmission element is not reduced in thickness to wire cross-section over its full circumference, as in the prior art, but is reduced in such a way that the force transmission element still extends over the entire inner diameter of the shaft in the flattened regions.
Accordingly, the force transmission element comprises webs or band-like sections in the flattened regions. The flattened regions may also consist of incisions in the force transmission element, that extend transversely to the lengthwise axis and also transversely to the plane of curvature, the force transmission element otherwise being preferably made of solid material. The configuration of the force transmission element with flattened sections in the region of the bend gives the force transmission element flexibility in the plane of curvature, which is absolutely sufficient since the bend of the shaft only requires flexibility of the force transmission element in the plane of curvature. The configuration of the force transmission element with flattened sections in the region of the bend and the extension of those sections over the inner diameter of the shaft provides, however, the advantage that the force transmission element offers high stability in spite of the reduced material thickness in the region of the flattened sections since it is exactly those sections that extend over the full width of the shaft. Consequently, contrary to the instrument known from the before-mentioned DE 195 20 717 C2, where the force transmission element is reduced to wire cross-section over the full circumference in the region of the bend of the shaft, a force transmission element, which is strong in the region of the bend, is thereby provided even in cases of miniaturized configuration of the instrument with a very small shaft diameter.
The intermediate sections between the flattened sections ensure that the force transmission element is guided with small play in the shaft, in the region of the bend, and prevent any buckling of the force transmission element in the region of the bend in the plane of curvature.
It is further preferred in this context if the flattened sections of the force transmission element are formed from solid material by a machining process where the flattened sections may be formed, for example by a milling operation, by removing material from two circumferential opposite sides of the force transmission element in a direction transversely to the lengthwise direction of the force transmission element. This also simplifies the manufacture of the force transmission element, compared with the force transmission element of the known instrument, since in the latter case the circumferential grooves must be formed by a turning operation on a lathe.
According to another preferred embodiment, each of the flattened sections is formed at the same axial position from two opposite sides of the circumference of the force transmission element.
This feature provides the advantage that central areas in the form of flat bands can be formed relative to the lengthwise axis of the force transmission element, for which the maximum diameter of the force transmission element is available.
According to an alternative preferred embodiment, the flattened sections are formed in axially offset arrangement from opposite sides of the circumference of the force transmission element.
In the case of this embodiment, the flattened portions are provided in alternating arrangement at offset circumferential positions, similar to a meander, which provides the advantage that while being likewise flexible in cross-section in the unilaterally flattened sections, the force transmission element nevertheless offers high stability.
In a third aspect of the invention, the object underlying the invention is achieved by a medical instrument for dissecting tissue in the human or animal body, comprising:
a shaft having a distal end and a proximal end, said shaft having at least one bend between said distal and said proximal end;
at least one movable tool disposed at said distal end of said shaft;
at least one movable grip element disposed at said proximal end of said shaft;
a force transmission element having a distal end a proximal end and extending along said shaft and, further, being movable relative to said shaft, said proximal end of said force transmission element being operatively interconnected to said at least one movable grip element and said distal end of said force transmission element being operatively interconnected to said at least one movable tool for transmitting a force from said at least one movable grip to said at least one movable tool;
said force transmission element being configured, at least in the region of said bend and continuously in axial direction, as an axially flat band extending in the region of said bend in direction transversely to a plane of curvature of said bend, wherein narrow sides of said bend are guided in lateral guides in said shaft.
This medical instrument according to a third aspect of the present invention provides the advantage that the flexible configuration of the force transmission element in the region of the bend of the shaft is particularly simple, both in terms of design and manufacturing technique. By having the narrow sides guided in lateral guides in the shaft any buckling of the force transmission element in the region of the bend is prevented in this case as well.
It is preferred in this connection if the guides are formed as grooves in an inner wall of the shaft.
This feature provides the advantage that the shaft can be closed in the region of the bend whereby any penetration of contaminants into the shaft can be avoided.
Alternatively, it is however also preferred if the guides are configured as open slots in the shaft.
This feature provides the advantage that the slots can be introduced into the shaft in an especially simple way, in terms of manufacturing technique, so that the manufacturing expense of the instrument is reduced in the case of this embodiment.
According to a further preferred embodiment of all the aforementioned instruments, the force transmission element is configured as a solid bar, consisting of solid material, in regions outside the bend.
It is an advantage of this arrangement that the force transmission element can be made especially strong and rigid in regions outside the at least one bend, especially over elongated straight regions of the shaft, which makes the force transmission element particularly well suited for the transfer of high thrust.
According to another preferred embodiment, the flat band of the instrument according to the third aspect of the invention is formed from the bar by a machining operation.
This feature provides the advantage that the flat band and the remaining body of the force transmission element are made as a single piece, whereby any predetermined breaking points, for example in the form of soldering, welding or bonding points, can be avoided.
Alternatively, it is however also preferred if the band is connected with the bar by a substance bond.
This is of advantage in cases where it is meaningful for reasons of manufacturing technique to produce the bar and the band by separate processes.
According to another preferred embodiment of the instruments according to all of the three aspects, the at least one movable tool is axially movable relative to the shaft, and a second tool is arranged at the distal end of the shaft, the movable tool and the second tool acting together in the way of a punch if moved axially one relative to the other.
Such an embodiment offers the advantage, especially if used in very restricted operating regions, for example in the frontal or maxillary sinus, that the two tools do not need a free operating radius beyond the circumference of the shaft, for dissecting tissue, because both tools are moved relative one to the other only in the axial direction of the shaft, or more precisely, in the lengthwise direction of the distal end of the shaft.
It is further preferred in this connection if the second tool is connected with the shaft immovably, and is arranged distally before the movable tool.
This arrangement provides the advantage that the second immovable tool forms the distal point of the shaft and defines a stationary working point when that immovable tool is applied to the tissue to be dissected. In this case, thrust is exerted by the force transmission element to displace the movable tool in distal direction relative to the immovable tool, in order to cut off the tissue gripped between the immovable tool and the movable tool, and a pull force is exerted for the purpose of separating the two tools again one from the other.
According to another preferred embodiment, the at least one movable tool is protected from torsion relative to the second tool.
This feature is of advantage especially in connection with that medical instrument which has the force transmission element configured as a tube and as a helical spring in the region of the bend. The protection from torsion retains the movable tool and the second tool in fixed positions one relative to the other, with respect to torsion about the longitudinal axis of the shaft, and this even under rotary forces acting on the helical spring.
As an alternative to the configuration of the at least one movable tool as punching tool, the invention can be used, however, with like advantage if the at least one movable tool is configured as a jaw part which can be pivoted about a hinge joint and which coacts with a second tool in the manner of a pair of scissors or a forceps.
Further advantages are evident from the description below and the appended drawings.
It is understood that the features recited above and those yet to be explained below can be used not only in the respective combination indicated, but also in other combinations or in isolation, without leaving the scope of the present invention.